This Stage II CEBRA application involves the development of Neurochem Chip microelectrodes for neurochemical recordings of neurotransmitter release in rats and mice. The long-term goals of this project are to develop Neurochem Chips for rapid in vivo recordings of glutamate, GABA, acetylcholine and choline in the CNS of freely moving rats and mice. In developing the technologies, we will first implement and improve the technologies of Neurochem Chips in rats and mice. First, we plan to optimize the recording approaches in the anesthetized rat and mouse. This will involve microelectrode development in corporation with Thin Film Technologies, Hybrid Circuits, Inc., and Cleveland Medical Devices, Inc. Instrumentation development will occur in cooperation with PCB Assembly, Inc. We will carry out extensive in vitro and in vivo recordings of glutamate, GABA, choline and acetylcholine release and uptake in the prefrontal cortex, striatum and hippocampus of anesthetized rats. There are numerous microelectrode, instrumentation, and recording details that must first be optimized to develop reliable Neurochem Chips. These microelectrodes recordings will be compared with microdialysis measures of glutamate and choline, to try and further validate the techniques. As this grant progresses, the refined and adapted technologies will be applied to studies in awake behaving rats and mice. Freely moving tethered systems will be developed for 4-channel measures in awake rats and 2-channel recordings in mice. In addition, a biotelemetric system will be developed to record from rats with a totally untethered system. This should contribute to 1) increased signal-to-noise of the recordings, 2) increased freedom of movement of the rats, and 3) the potential for monitoring large numbers of rats. The major goal of these studies is to develop Neurochem Chips that are reliable, sensitive and selective for the rapid (second-by-second) determination of neurochemicals in the extracellular space of the brain. This technology could have a major impact on basic science studies of neurotransmitter systems involving drug abuse, disease models and behavior. This CEBRA Stage II mechanism is needed, due to the number of technical issues that must be addressed before these techniques can be disseminated to other researchers.